Research progress of pore-throat structure in tight sandstone formation

The physical properties and the seepage characteristics of oil, gas and water in tight sandstone reservoir are significantly determined by occurrence, size distribution and connectivity of pore-throat structure. In this paper, the principle, characteristics and applicability of image analysis technology and inversion analysis technology including 10 kinds of the main pore-throat structure analytical techniques were summarized; the characteristics and characterizing methods of pore-throat size, fractal, connectivity and network structure were analyzed; and the research tendency of dynamic pore-throat structure characteristics based on various stress and enhance oil recovery technology based on pore-throat structure characteristics was estimated. Due to the complexity of pore-throat size distribution and pore-throat structure of tight sandstone, a variety of testing techniques and characterization methods should be adopted to achieve the comprehensive and accurate determination of pore-throat structure. During the development, as a decrease of reservoir pressure, the pore-throat structure changes dynamically. Moreover, the seepage and development are determined by the large throats and pore volume connected by large throats. Decreasing the cutoff throat radius is an important way to improve the sweep efficiency of throat and the development efficiency of tight reservoir. The characterization method of dynamic pore-throat structure and its corresponding seepage characteristics as well as the method to decrease the cutoff throat radius still need to be further studied in the future.